Effect of CaF2/CaO Composite Additive on Roasting of Vanadium-Bearing Stone Coal and Acid Leaching Kinetics

Bo Wang,Yimin Zhang,Jing Huang,Tao Liu

doi:10.3390/min7030043

Abstract

In this paper, the composite additive of CaF2/CaO was used to extract vanadium from stone coal, and the effect of roasting and leaching kinetics were studied. The purpose of this manuscript is to realize and improve the vanadium recovery from stone coal using the composite additive. The experimental results indicated that the roasted clinker can be obtained under the conditions of CaF2/CaO at a mass ratio of 2:3 and a total additive amount of 10 wt %, a roasting temperature 850 °C, and a roasting time of 90 min. The leaching rate of vanadium can reach 86.74%, which increased by 16.4% compared with that of blank roasting under the conditions including a leaching temperature of 950 °C, a sulfuric acid concentration of 15% (v/v), a leaching time of 2 h, and a ratio of liquid to solid of 3 mL/g. The phase transformation analysis indicated that the muscovite structure was effectively destroyed during the roasting process comparing with no additives, which provided the basis for vanadium dissociation. Roasting can promote the formation of calcium vanadate, which is beneficial to the leaching of vanadium. The vanadium leaching kinetic analysis indicated that the activation energy of the acid leaching reaction decreased from 42.50 KJ/mol in the blank roasting to 22.56 KJ/mol in the calcified roasting, and the reaction order, with respect to the sulfuric acid concentration, decreased from 1.15 to 0.85. Calcified roasting has a better mineral activation than blank roasting, which can accelerate the leaching of vanadium and reduce the dependence on high-temperature and high acid levels in the leaching process.

Highlights

Vanadium is a significant strategic resource which plays an important role in many fields, such as ferrous and nonferrous alloy production, thermistors, redox flow batteries, catalysts, the chemical industry, and medicine [1,2,3,4,5]
The vanadium leaching rate increased from 70.34% in the blank roasting to 86.74% in the calcified roasting under the conditions including leaching temperature of 95 ◦ C, the sulfuric acid concentration of 15% (v/v), leaching time of 2 h, and ratio of liquid to solid of 3 mL/g
According to phase transformation analysis, the muscovite structure was effectively destroyed during the composite CaF2 /CaO roasting process, which could provide the basis for vanadium dissociation and promote the formation of calcium vanadate

Summary

Introduction

Vanadium is a significant strategic resource which plays an important role in many fields, such as ferrous and nonferrous alloy production, thermistors, redox flow batteries, catalysts, the chemical industry, and medicine [1,2,3,4,5]. The all-wet process vanadium extraction process is very selective to the ore. It is only suitable for the oxidized stone coal with a high valence state and adsorption state, and it is necessary to destroy the lattice structure of vanadium-containing silicate minerals under the condition of high acid concentration or high temperature and high pressure, and the production cost is high [12]. The calcified roasting acid leaching process is a roasting–wet extraction of vanadium in a way. Calcified roasting is a type of low-pollution and environmentally-friendly roasting process [14], but it still faces the problem that the calcium-containing additive causes limited damage to the crystal structure of vanadium-containing minerals, and the vanadium leaching rate is low

Methods

Results

Conclusion